Symmetry change in LaNiO3 films caused by epitaxial strain from LaAlO3, SrTiO3, and DyScO3 pseudocubic (001) surfaces.

To elucidate the epitaxial strain effect over a wide range of lattice mismatch, we investigated the structures of ∼ 25 nm thick LaNiO 3 films grown on the pseudocubic (001) surfaces of three different substrates, namely, LaAlO 3 (LAO), SrTiO 3 (STO), and DyScO 3 (DSO). Such structural information had been inferred from the intensities of a small number of Bragg reflections that relate to the NiO 6 octahedral tilting in previous studies. Here, we measured more than 100 reciprocal lattice points to derive reliable structural information. The procedure of ordinary crystal structure analysis is hampered by the multidomain structure and limited volume of measurable reciprocal space, both caused by a huge, highly symmetric substrate. To overcome this difficulty, we employed the Bayesian inference to obtain the detailed atomic positions in film samples. Octahedral tilting about the c axis was dominant for the compressively strained film grown on LAO, whereas tilting about the a and b axes was dominant for the tensile strained films grown on STO and DSO. The film lattice parameters of the samples grown on STO and DSO were nearly identical, whereas additional twofold lattice modulation, including cation displacement, was only observed in the latter. [ABSTRACT FROM AUTHOR]